PsyVoidPsyFun
 Psyker Build - Warhammer 40k: Darktide 

When in doubt, press F. If you have doubt, press F. If you haven't pressed F yet, press it now. Will you explode? maybe, but it will be worth it.

Illisi
Perks:

• Flak - common armor type you will have to deal with in melee that you can't just one shot.
• Maniac - (lets you one shot Mutants on special crits, which during your ult will happen often)

Blessings:

• Shred - already a decent blessing, but with all the increased crit, and crit damage from Keystone/Ability this is fabulous. Also helps give a ton of Toughness with Mettle.
• Unstable Power - you will always be courting death from self brain pop - so you will almost always benefit from this to its full extent helping to one shot Mutants and elites without having to stack from hordes. Slaughterer and Uncanny are both good alternatives.

Voidstrike
Perks: 

• Crit - More crit = more surge = more death. Flak is fine post nerfs as it can help headshot Gunners when your ult is down... but it should rarely be down so just get used to pressing F.
• Unyielding - the only thing you can't one shot with Void + Surge are bosses, so might as well hit them harder. This is still true even after nerfs, you do need some Disrupt Destiny and Gaze stacks now. Carapace is a fine option as it makes it easier to one shot Bulwark through shield and Crushers post nerfs. 

Blessings:

• Transfer Peril - This allows you to spam the staff during ult with very few peril problems for the first 10-15 seconds of ult.
• Surge - You will have huge crit chance during ult (7.5% crit base, 15% from weapon and talents +  20% from ult) and an occasional free crit from True Aim your damage is going to be crazy. 
   

Scrier's Gaze
To be used at all time - we are running max CD so anytime it goes down we can get it back as soon as possible to continue the rampage. It turns the normally weak (in melee) Psyker into a juggernaut of doom, wading into the enemies in ways that will make your Ogryn blush. 
OR* you can pull out your Voidstrike and obliterate the map for the next 15~ seconds depending on how long the enemies are able to keep twitching for the juicy Transfer Peril, and Battle meditation procs to keep your peril levels neutral with Reality Anchor. Precognitionis more damage, but not generally worth it means your ult will not last as long particularly when you are using Voidstrike.

Disrupt Destiny
This gives even more finesse damage (crit and Weakpoint) more toughness regen, and more damage.
Lingering influence allows you to keep the stacks, specially when your try hard pub allies are trying to take all the kills. Perfectionism is fine - higher damage cap but much less consistent.
Cruel Fortune will let you get to max stacks quickly when you get into hordes.

You can replace toughness with Perilous Combustion on Auric - since that is the only source of SoulBlaze there has to be a lot of Elites/Specials to make it worth taking. 

Also consider going for Seer's Presence so you can get One with the Warp if you are having difficulty surviving. With some TDR nodes you can get over 50% TDR at high peril which should happen often with Gaze, Kinetic Deflection and your force weapons. You can also swap -Peril Gen for more Toughness nodes, or TDR

Note - you will see I never mentioned Smite - that is because you will never use it in this build. None of the other blitz abilities would give you anything that Voidstrike can't do and it is just better situated for getting the nodes you want.